nsupdate and round robin

Kevin Darcy kcd at daimlerchrysler.com
Mon Jan 8 21:59:03 UTC 2007

Victor Hugo dos Santos wrote:
> 2007/1/4, Mark Andrews <Mark_Andrews at isc.org>:
>>> Victor Hugo dos Santos wrote:
>>>> 2007/1/2, Kevin Darcy <kcd at daimlerchrysler.com>
> [...]
>>> OK, I see what you're saying now. The client's address changes and it
>>> wants to delete the previous address and add the new address. There's no
>>> convenient way to do that currently within the widely-deployed DNS
>>> protocol, that's what http://www.rfc-editor.org/rfc/rfc4701.txt is all
>>> about, but apparently BIND does not yet support that RR type. I don't
>>> know that any DHCP clients natively support DHCID either, but then I
>>> haven't researched the subject in any depth.
>>         Current named's and nsupdate's will handle DHCID just fine.
>>         They will just treat it as a unknown type until you update
>>         to BIND 9.5 which knows about DHCID.
> cool.. DHCID is exactly the option what i needed....but, where is
> documentation about this ??? I was reading the RFCs (4701), but theu
> are not very clear !!!
I should have probably also given you a reference to the companion RFC, 
http://www.rfc-editor.org/rfc/rfc4703.txt. Hopefully that should make 
things clearer.

If you need more "user-level" documentation than that, then, since as I understand it (probably not very well), DHCID is something that is used primarily by DHCP clients, your best bet would probably be to look at your DHCP client documentation, if it already has DHCID capability. If it doesn't, then you need to consider switching to a different DHCP client, getting a third-party modification to your client, or modify your DHCP client yourself. If you're going to implement this yourself, then the RFC(s) already cited should give one sufficient information to accomplish the task (complain to the RFC author(s) if that isn't the case :-)

When I said that BIND didn't support DHCID, I was basing this on the 
fact that it doesn't recognize a DHCID RR in a master zone file. But, 
this was misguided, since DHCID is intended exclusively for *dynamic* 
records, one would never been hand-editing DHCID records into a master 
zone file, thus it is sufficient -- as Mark pointed out -- that named 
and/or nsupdate can handle it properly as an "unknown" type. So, please 
disregard my previous statement about BIND not supporting DHCID...

                           - Kevin

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